In the above amplitudes, we assume that all the short ranged interactions could be fully absorbed into a single form factor as in Refs. 
[1]}, [2]}, [3]}, [4]}, [5]}, [6]}, [7]}, [8]}, [9]}, which is also introduced to depict the internal structures of the exchanged mesons. Moreover, the form factor also plays a role of removing the divergences in the amplitudes. Here, the form factor is in the form  [1]}, [2]}, [3]}, [4]}, [5]}, [6]}, [7]}, [8]}, [9]},
\(\mathcal {F}(q^2,m_q^2)= \frac{m_q^2-\Lambda ^2}{q^2-\Lambda ^2},\) 
